Luminescent apparatus and method of manufacturing the same

ABSTRACT

The present invention provides a luminescent apparatus having a bright, high-quality image. A reflecting surface-including electrode, and an EL element formed of an organic EL layer and a transparent electrode are provided on an insulator. As shown in FIG.  1 , an auxiliary electrode  107  formed of a transparent conductive film is connected to the transparent electrode via a conductor. This structure enables a resistance value of the transparent electrode  104  to be substantially lowered, and a uniform, voltage to be applied to the organic EL layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 09/851,656, filed on May 8, 2001 U.S. Pat. No. 6,608,449, nowallowed, which claims the benefit of a foreign priority applicationfiled in Japan on May 8, 2000 as Ser. No. 2000-135076, both of which areincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a luminescent apparatus using a thin film madeof a luminescent material, and also to an electric appliance using theluminescent apparatus as a display. An organic EL display and an organiclight-emitting diode (OLED) are included in the luminescent apparatusaccording to the present invention.

The luminescent materials which can be used for the present inventioninclude all luminescent materials that emit light (phospholescenceand/or fluorescence) via singlet excitation or triplet excitation orboth thereof.

2. Description of the Related Art

In recent years, the development of a luminescent element (hereinafterreferred to as EL element) using a thin film (hereinafter referred to asEL film) made of a luminescent material capable of obtaining EL(electroluminescence) has been forwarded. A luminescent apparatus(hereinafter referred to as EL luminescent apparatus) has an EL elementhaving a structure in which an EL film is held between an anode and acathode. This apparatus is adapted to obtain luminescence by applying avoltage between the positive and cathode. Especially, an organic filmused as an EL film is called an organic EL film.

A metal (typically, a metal of Group I or II on the, periodic table)having a small work function is used as a cathode in many cases, while aconductive film (hereinafter referred to as a transparent conductivefilm) transparent with respect to visible light is used as an anode inmany cases. Owing to such a structure, the luminescence obtained passesthrough the anode, and is visually recognized.

Recently, the development of an active matrix type EL luminescentapparatus adapted to control the luminescence of an EL element providedin each image element by using a TFT (thin film transistor) has beenforwarded, and a prototype thereof has come to be made public. Theconstructions of active matrix type EL luminescent apparatuses are shownin FIGS. 9A and 9B.

Referring to FIG. 9A, a TFT 902 is formed on a substrate 901, and ananode 903 is connected to the TFT 902. An organic EL film 904 and acathode 905 are formed on the anode 903, and an EL element 906 includingthe anode 903, organic EL film 904 and cathode 905 is thereby formed.

In this luminescent apparatus, the luminescence generated in the organicEL film 904 passes through the anode 903, and is emitted in thedirection of an arrow in the drawing. Therefore, the TFT 902 becomes aluminescence screening object from an observer's viewpoint, and causesan effective emission region (region in which an observer can makeobservation of luminescence) to be narrowed. In order to obtain a brightimage when the effective emission region is narrow, it is necessary toincrease an emission brightness but increasing the emission brightnessresults in an early deterioration of the organic EL film.

Under these circumstances, an active matrix type EL luminescentapparatus of a structure shown in FIG. 9B has been proposed. Referringto FIG. 9B, a TFT 902 is formed on a substrate 901, and a cathode 907 isconnected to the TFT 902. An organic EL film 908 and an anode 909 areformed on the cathode 907, and an EL element 910 including the cathode907, organic EL film 908 and the anode 909 are thereby formed. That is,this EL element 910 constitutes a structure directed contrariwise withrespect to the EL element 906 shown in FIG. 9A.

In the luminescent apparatus of FIG. 9B, the luminescence generatedtheoretically in the EL film 908 passes through the anode 909, and isemitted in the direction of an arrow in the drawing. Accordingly, theTFT 901 enables the whole region, which is provided in a position whichcannot be seen by an observer, and which has the electrode 907 thereon,to be used as an effective emission region.

However, the structure shown in FIG. 9B has potentially a problem thatthe structure is incapable of applying a uniform voltage to the anode909. It is known that a resistance value of a transparent conductivefilm used generally as an anode is high as compared with that of ametallic film and can be reduced by thermally treating the transparentfilm. However, since the organic EL film has a low thermal resistance, athermal treatment of over 150° C. cannot be conducted after the organicEL film has been formed.

Therefore, when an anode (transparent conductive film) is laminated onan organic EL film, a thermal treatment cannot be conducted, so that itis difficult to form an anode of a low resistance value. That is, thereis a possibility that a level of a voltage applied to the anode differsat an end portion and a central portion thereof. There is a fear thatthis problem causes a decrease in the quality of an image.

As mentioned above, in a luminescent apparatus including a structureusing a transparent conductive film formed after the formation of anorganic EL film, it is difficult to reduce the resistance of thetransparent conductive film.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstances,and it is an object of the invention to provide a luminescent apparatuscapable of displaying a bright, high-quality image, and also an electricappliance using such a luminescent apparatus as a display and capable ofdisplaying an image of a high quality. The present invention will bedescribed with reference to FIG. 1.

According to an aspect of the present invention, the method ofmanufacturing a luminescent apparatus has the step of connecting anauxiliary electrode to a transparent electrode, which is provided afterthe formation of an organic EL film, in parallel therewith so as tosubstantially reduce the resistance of the transparent electrode.

Referring to FIG. 1, a reference numeral 101 denotes an insulator, 102an electrode including a reflecting surface, 103 an organic EL layer,and 104 an electrode (hereinafter referred to as transparent electrode)transparent or translucent with respect to the visible light. On theinsulator 101, an EL element formed of the electrode 102 including areflecting surface, organic EL layer 103, and transparent electrode 104is formed.

The phrase “transparent with respect to the visible light” means thatthe visible light is transmitted with a transmission factor of 80–100%.The phrase “translucent with respect to the visible light” means thatthe visible light is transmitted with a transmission factor of 50–80%.Although the transmission factor differs depending upon the thickness ofa film, of course, the thickness of a film may be designed suitably sothat the transmission factors be within the above-described range.

The insulator 101 may be formed of an insulating substrate or asubstrate provided with an insulating film on a surface thereof as longas it can support the EL element.

The electrode 102 including a reflecting surface means a metallicelectrode or an electrode formed of a lamination of a metallic electrodeand a transparent electrode. That is, the electrode 102 means anelectrode including a surface (reflecting surface) capable of reflectingthe visible light on an outer surface or a rear surface thereof or aninterface in the interior thereof.

The organic EL layer 103 used can be formed of an organic EL film or alaminated film of an organic EL film and a film of an organic material.That is, an organic EL film may be provided singly as a luminescentlayer, or a layer of an organic material as a charge-injected layer or acharge carrying layer may be laminated on an organic EL layer as aluminescent layer. The inorganic materials include a material capable ofbeing used as a charge-injected, layer or a charge carrying layer, and alayer of such an inorganic material can also be used as acharge-injected layer or a charge carrying layer.

The transparent electrode 104 can be formed of an electrode of atransparent conductive film or an electrode of a metallic film(hereinafter referred to as a translucent metallic film) of 5–70 nm(typically, 10–50 nm) in thickness. The transparent conductive film canbe formed of a conductive oxide film (typically, an indium oxide film, atin oxide film, a zinc oxide film, a compound film of indium oxide andtin oxide, a compound film of indium oxide and zinc oxide), or amaterial obtained by adding gallium oxide to a conductive oxide film.When a transparent conductive film is used as the transparent electrode104, its thickness is set to 10–200 nm (preferably 50–100 nm), and thisenables the electrode to transmit the visible light with a transmissionfactor of 80–95%.

On the EL element 105 formed of the above-described structure, a sealmember 106 and an auxiliary electrode 107 are provided, and theauxiliary electrode 107 is electrically connected to the transparentelectrode 104 via anisotropic conductors 108. The anisotropic conductors108 scattering on the transparent electrode 104 are preferably providedso that they are distributed over the whole surface thereof.

The seal member 106 is a substrate or a film transparent with respect tothe visible light, and a glass substrate, a quartz substrate, acrystallized glass substrate, a plastic substrate, or a plastic film canbe used. When a plastic substrate or a plastic film is used, it ispreferable to provide an outer surface of a rear surface thereof with aprotective film (preferably a carbon film, specifically a diamond-likecarbon film) capable of preventing the passage of oxygen and watertherethrough.

The auxiliary electrode 107 is an electrode provided auxiliarily for thepurpose of reducing a resistance value of the transparent electrode 104,and can be made of an electrode formed of a transparent conductive filmor an electrode formed of a translucent metallic film just as thetransparent electrode 104. When the thickness of the auxiliary electrode107 is set to 10–200 nm (preferably 50–100 nm) in the same manner asthat of the transparent electrode 104, the auxiliary electrode cantransmit the visible light with a transmission factor of 80–95%.

The anisotropic conductors 108 can be formed by using anisotropicconductive films. The anisotropic conductive film is a resin film inwhich conductive particles (typically metallic particles or carbonparticles) are dispersed uniformly. According to the present invention,it is preferable that the anisotropic conductive films 108 be providedselectively by patterning them by photolithography, by an ink jetmethod, or a printing method. The reason resides in the low transmissionfactor of the anisotropic conductive film with respect to the visiblelight. Therefore, when the anisotropic conductors are provided over thewhole surface of the transparent electrode 104, the light emitted fromthe organic EL layer 103 is absorbed thereinto.

In the luminescent apparatus including the above-described structuresaccording to the present invention, the auxiliary electrode 107functions as an electrode connected to the transparent electrode 104,which is formed of a transparent conductive film, in parallel therewith.Since the auxiliary electrode 107 is formed on the side of the sealmember 106, a resistance value can be reduced to a low level withoutbeing restricted by the low thermal resistance of the organic EL filmreferred to in the descriptions of the related art examples. Therefore,when the present invention is put into practice, it becomes possible toapply a uniform voltage to the transparent electrode 104 and obtain animage of a high quality.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described indetail on the basis of the following figures, wherein:

FIG. 1 is a drawing showing in section the construction of a luminescentapparatus;

FIGS. 2A and 2B are drawings showing in section the construction of aluminescent apparatus;

FIGS. 3A–3E are drawings showing the steps of manufacturing aluminescent apparatus;

FIGS. 4A–4D are drawings showing the steps of manufacturing aluminescent apparatus;

FIGS. 5A and 5B are drawings showing the construction of an uppersurface of a pixel of a luminescent apparatus and the construction of acircuit thereof;

FIG. 6 is a drawing showing in section the construction of a retentioncapacitor;

FIG. 7 is a drawing showing in section the construction of a luminescentapparatus;

FIGS. 8A and 8B are drawings showing the construction of an uppersurface of the luminescent apparatus; and

FIGS. 9A and 9B are drawings showing the construction of related artluminescent apparatuses.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A mode of embodiment of the present invention will now be described withreference to FIG. 2. Referring to FIG. 2, a reference numeral 201denotes a substrate on which elements are formed. According to thepresent invention, any material may be used for the substrate 201. Thatis, glass (including quartz glass), crystallized glass, monocrystallinesilicon, a ceramic material, a metal, or a plastic can be used.

A pixel 202 is formed on the substrate 201, and has a structureincluding a switching TFT 203 and a current control TFT 204. FIG. 2shows three pixels emitting red, green, or blue light respectively. Theswitching TFT 203 functions as a switch to input video signals into thepixels, and the current control TFT 204 functions as a switch forcontrolling a current flowing in an EL element. In this embodiment, adrain of the switching TFT 204 is electrically connected to a gate ofthe current control TFT 204.

Limitations are not placed on the construction of the switching TFT 203and current control TFT 204. A top gate type (typically, a planar type)TFT or a bottom gate type (typically, an inversely staggered type) TFTmay be used. An n-channel type TFT or a p-channel type TFT may be usedfor both of these TFTs.

The switching TFT 203 and current control TFT 204 are covered with aninter-layer insulating film 205, to an upper portion of which a pixelelectrode 207 formed of a metallic film and a drain of the currentcontrol TFT 204 are electrically connected via anisotropic conductiveplugs 206. On the pixel electrode 207, a first transparent electrode 20810–200 nm (preferably 50–100 nm) thick is laminated. In this embodiment,the pixel electrode 207 and first transparent electrode 208 form ananode 230.

This mode of embodiment employs a structure in which contact holes inwhich the drain of the current control TFT 204 and pixel electrode 207are connected together are filled with anisotropic conductors. Theseanisotropic conductors provided so as to fill the contact holestherewith are called anisotropic conductive plugs. The anisotropicconductive plugs 206 may be formed by etching an anisotropic conductivefilm. Of course, the pixel electrode 207 may be connected directly tothe drain of the current control TFT 204.

In recesses due to these contact holes, the coverage of the organic ELlayers is poor, and there is a fear of causing short-circuiting of thecathode and the anode, so that such recesses are not desirable. In thismode of embodiment, the formation of the recesses due to the contactholes of the pixel electrode 207 can be prevented by using theanisotropic conductive plugs 206, and this enables the prevention of theoccurrence of the short-circuiting of the cathode and the anode.

The pixel electrode 207 is formed preferably by using a metallic film ofa high reflectance, such as an aluminum, film (including an aluminumalloy film and an additive-containing aluminum film), or a thin silverfilm. A film formed by coating a metallic film with aluminum or silvermay also be used.

A reference numeral 209 denotes insulating films (hereinafter referredto as banks) provided between portions of the anode 230, and formed soas to cover level-different portions at end sections of the anode 230.In this mode of embodiment, the provision of the banks 209 keeps theorganic EL layers away from end sections of the anode 230 which areliable to give rise to field concentration, and the deterioration, whichis ascribed to the field concentration, of the organic EL layers isthereby prevented. The banks 209 may be formed by using either resinfilms or silicon-containing insulating films (typically, a silicon oxidefilms).

A reference numeral 210 denotes an organic EL layer emitting red light,211 an organic EL layer emitting green light, and 212 an organic ELlayer emitting blue light. The construction of the organic EL layers210-212 may be selectively determined with reference to knowntechniques.

A second transparent electrode 213 provided so as to cover the organicEL layers 210–212 is an electrode for injecting electrons into theorganic EL layers. A work function of this second transparent electrode213 is preferably 2.5–3.5 eV, and this electrode may be formed by usinga metallic film containing an element belonging to Group I or II on theperiodic table. In this embodiment, an alloy film (hereinafter referredto as Al—Li film) formed by coevaporating aluminum and lithium. Sincethe Al—Li film is a metallic film, it can be used as a transparentelectrode by setting its thickness to 10–70 nm (typically, 20–50 nm).

On this second transparent electrode a third transparent electrode 214formed of a 100–300 nm (preferably 150–200 nm) thick transparentconductive, film is provided. The third transparent electrode 214 is anelectrode adapted to fulfill the function of applying a voltage to thesecond transparent electrode 213. In this embodiment, the second andthird transparent electrodes 213, 214 form together a cathode 231.

A seal member 215 provided so as to be opposed to the substrate 201(which is called in this embodiment a substrate including a thin filmprovided on the substrate 201) has an auxiliary electrode (fourthtransparent electrode) 216 formed thereon which is made of a transparentconductive film 10–200 nm (preferably 50–100 nm) thick. The thirdtransparent electrode 214 and the auxiliary electrode 216 areelectrically connected together via anisotropic conductors 217 each ofwhich is formed of an anisotropic conductive film (resin film in whichmetallic particles or carbon particles are dispersed).

It is preferable that the anisotropic conductors 217 be providedpartially on the third transparent electrode 214. That is, it isdesirable that the anisotropic conductive film be provided so as not tobe superposed on at least an emission region of the pixels since thisfilm is black or gray. When the anisotropic conductive film is usedpositively as a black matrix by providing the same among pixels, theoptical directivity of each pixel can, of course, be improved.

The substrate 201 and seal member 215 are pasted on each other by asealant (not shown) provided on outer edge portions of the substrate201. When the substrate 201 and the seal member 215 are pasted on eachother, a spacer (preferably 1–3 μm thick) for defining a clearancebetween the substrate 201 and the seal member 215 may be provided.Especially, providing the anisotropic conductors 217 so that they servealso as spacers is effective.

It is preferable that a nitrogen gas or a rare gas be sealed in a space218 formed between the substrate 201 and the seal member 215. It isdesirable to provide this space 218 with a material having ahygroscopicity or a material having deoxidization characteristics.

The detailed construction of a region 219 is shown in FIG. 2B. Referringto FIG. 2B, an anode 230, an organic EL layer 212, and a cathode 231form an EL element 220. The most characteristic point of the luminescentapparatus shown in FIG. 2A resides in that the emission of light isobserved through the cathode 231.

Out of the light generated in the EL element 220, the light advancingtoward the anode 230 is reflected on the pixel electrode 207 having asurface of a high reflectance, and the resultant light advances towardthe cathode 231. That is, the pixel electrode 207 is an electrodeadapted to supply (extract electrons) a current to the anode 230, andalso having a function of a reflector.

Since the second transparent electrode 213 has an extremely smallthickness, a resistance value thereof is high. Therefore a thirdtransparent electrode 214 is laminated on the electrode 213 so as tolower the resistance value of the latter. However, since the transparentconductive film used for the third transparent electrode 214 is formedafter the organic EL layer has been formed, it is difficult to lower theresistance value of the second transparent electrode. Therefore, in thismode of embodiment, the auxiliary electrode 216 made of a transparentconductive film is connected to the third transparent electrode 214,which is made of a transparent conductive film, in parallel therewith soas to substantially reduce the resistance of the third transparentelectrode 214.

In the luminescent apparatus of the above-described construction, apixel as a whole forms an effective emission region, so that a verybright image can be obtained. When the present invention is put intopractice, a uniform voltage can be applied to the cathode as a whole,and this enables an image of a high quality to be obtained.

[Embodiments]

[Embodiment]1

In this embodiment, the steps of manufacturing the luminescent apparatusshown in FIG. 2 will be described with reference to FIGS. 3–5. FIGS. 3and 4 are sectional views showing the steps for manufacturing a pixelportion. A top view (of the condition at a point in time at which ananode has been just formed) of a pixel formed according to thisembodiment is shown in FIG. 5A, and a circuit diagram of a final pixelin FIG. 5B. The reference numerals used in FIG. 5 correspond to thoseused in FIGS. 3 and 4.

First, as shown in FIG. 3A, a glass substrate 301 is prepared as asubstrate, and a base film 302 made of a silicon oxide film is formedthereon to a thickness of 200 nm. The forming of the base film 302 maybe done by using a low pressure thermal CVD method, a plasma CVD method,a sputtering method, or a vapor deposition method.

A crystalline silicon film 303 is then formed to a thickness of 50 nm onthe base film 302. A known method can be used as a method of forming thecrystalline silicon film 303. An amorphous silicon film may be lasercrystallized by using a solid state laser or an excimer laser, orcrystallized by a thermal treatment (furnace annealing). In thisembodiment, an amorphous silicon film is crystallized by irradiationwith an excimer laser beam using a XeCl gas.

Next, as shown in FIG. 3B, the crystalline silicon film 303 is patternedto form island-like crystalline films 304, 305. A gate insulating film306 made of a silicon oxide film is formed to a thickness of 80 nm so asto cover the island-like crystalline silicon films 304, 305. Gateelectrodes 307, 308 are further formed on the gate insulating film 306.According to the drawing, the gate electrode 307 is apparently formed oftwo separate parts but it is actually the same, bifurcated electrode.

In this embodiment, a tungsten film or a tungsten alloy film 350 nmthick is used as a material for the gate electrodes 307, 308. Otherknown materials can also be used, of course, as the materials for thegate electrodes. In this embodiment, a connecting wire 309 is alsoformed simultaneously with these gate electrodes. The connecting wire309 is a wire for electrically connecting a source of a current controlTFT and a current supply wire together later.

Next, as shown in FIG. 3C, an element (typically, boron) belonging tothe 13th group of the periodic table is added by using the gateelectrodes 307, 308 as masks. The adding of the element may be done by aknown method. Thus, impurity regions (hereinafter referred to as p-typeimpurity regions) 310–314 indicative of p-type conductive type regionsare formed. Just under the gate electrodes, channel-forming regions 315a, 315 b, 316 are defined. The p-type impurity regions 310–314constitute source regions or drain regions of the TFT.

The activation Of the element belonging to the 13th group of theperiodic table and added by conducting a thermal treatment is thencarried out. The pattern formed of the island-like crystalline siliconfilm subjected to various steps up to this activation step is called anactivated layer. This activation step may be carried out by furnaceannealing, laser annealing, lamp annealing, or a combination thereof. Inthis embodiment, a thermal treatment is carried out at 500° C. for 4hours in a nitrogen atmosphere.

In this activation step, it is desirable that oxygen concentration inthe treatment atmosphere be set not higher than 1 ppm (preferably nothigher than 0.1 ppm). The reasons reside in that, when the oxygenconcentration is high, the surfaces of the gate electrodes 307, 308 andthe connecting wire 309 are oxidized to cause it difficult to bringthese parts into electrical contact with a gate wire and a currentsupply wire which are to be formed later.

It is effective that a hydrogenation treatment be carried out after theend of the activation step. The hydrogenation treatment may be conductedby using known hydrogen annealing techniques or plasma hydrogenationtechniques.

As shown in FIG. 3D, a current supply line 317 is formed so that thissupply line contacts the connecting wire 309. When such a structure (atop view of which is shown in a region designated by 501 in FIG. 5A) isformed, the connecting wire 309 and the current supply wire 317 areelectrically connected together. During this time, a gate wire (shown ina region designated by 502 in FIG. 5A) is also formed at the same time,and electrically connected to the gate electrode 307. A top view of thisstructure is shown in a region designated by 503 in FIG. 5A.

In the region designated by 503, the gate wire 502 has a projectingportion, i.e., the gate wire 502 is redundantly designed so as to securea portion which does not get over the gate electrode 307. The reasonwhy, the gate wire 502 is formed in this manner resides in that, evenwhen the gate wire 502 is broken in the portion in which the gate wire502 gets over the electrode 307, the electrical breakage of the gatewire 502 in the mentioned portion can be avoided. The purpose of formingthe gate electrode 307 to the shape of the letter “C” is also toredundantly design the same so that a voltage is applied reliably toboth electrodes.

This current supply wire 317 and the gate wire 502 are formed of ametallic film the resistance of which is lower than those of theconnecting wire 309 and gate electrode 307. Preferably, a metallic filmcontaining copper or silver may be used. That is, a metallic film of ahigh processability is used for a gate electrode demanding a highpatterning accuracy, and a metallic film of a low specific resistancefor pass lines (gate wire and current supply wire in this embodiment)demanding a low specific resistance.

After the gate wire 502 and the connecting wire 309 have been formed, afirst interlayer insulating film made of a silicon oxide film is formedto a thickness of 800 nm. The forming of this film may be done by usinga plasma CVD method. Some other inorganic insulating film or a resin(organic insulating film) may be used as or for the first interlayerfilm 318.

Next, as shown in FIG. 3E, wires 319˜322 are formed by making contactholes in the first interlayer film 318. In this embodiment, metallicwires each of which is formed of a three-layer structure of titanium,aluminum, and titanium are used as the wires 319–322. Any materials may,of course, be used as long as they are in the form of conductive films.The wires 319–322 are used as source wires or drain wires of TFT.

The drain wire 322 of the current control TFT is electrically connectedto the connecting wire 309. As a result, the drain of a current controlTFT 402 and the current supply wire 317 are electrically connectedtogether.

A switching TFT 401 and current control TFT 402 are completed in thiscondition. Although both of these TFTs are formed of a p-channel typeTFT in this embodiment, both or either one of them may be formed of ann-channel type TFT.

The switching TFT 401 is formed so that the gate electrode crosses theactive layer at two portions thereof, and has a structure in which twochannel-forming regions are connected in series. When the TFT 401 isformed to such a structure, an off-current value (value of a currentflowing when the TFT is turned off) can be reduced effectively.

In the pixel, a holding capacitor 504 is formed as shown in FIG. 5A. Asectional view (taken along a line B–B′ in FIG. 5A) of the holdingcapacitor 504 is shown in FIG. 6. The holding capacitor 504 is formed ofa semiconductor layer 505 electrically connected to the drain of thecurrent control TFT 402, the gate insulating film 306 and a capacitorwire 506. That is, the semiconductor layer 505 and a capacitor wire 506are insulated by the insulating film 306, and form a capacitor (holdingcapacitor).

The capacitor wire 506 is formed simultaneously With the gate wire 502and current supply wire 317, and serves also as a wire for electricallyconnecting the gate electrode 308 and connecting wire 507 together. Theconnecting wire 507 is electrically connected to the drain wire (whichfunctions as a source wire in some cases) 320 of the switching TFT 401.

The advantage of the holding capacitor shown in this embodiment residesin that the capacitor wire 506 is formed after the active layer has beenformed. That is, since the semiconductor layer 505 constitutes a p-typeimpurity region in the case of this embodiment, it can be used as it isas an electrode.

After the wires 319–322 are formed, a passivation film 323 made of asilicon nitrogen film or a nitrided silicon oxide film is formed to athickness of 200 nm. When a hydrogenation treatment is conducted beforeor after this passivation film 323 is formed, the electriccharacteristics of the TFT can be improved.

As shown in FIG. 4A, a layer of an acrylic resin is then formed to athickness of 1 μm as a second interlayer insulating film 324. After acontact hole 325 is made, an anisotropic conductive film 326 is formed.In this embodiment, a layer of an acrylic resin in which silverparticles are dispersed is used as the anisotropic conductive film 326.It is desirable that the anisotropic conductive film 326 be formed tosuch a sufficient thickness that permits flattening the contact hole325. In this embodiment, the anisotropic conductive film 326 is formedto a thickness of 1.5 μm by a spin coating method.

The anisotropic conductive film 326 is then etched with plasma using anoxygen film. This process is continued until the second interlayerinsulating film 324 is exposed. When the etching of the film 326finishes, an anisotropic conductor plug 327 shown in FIG. 4B comes to beformed. When the second interlayer insulating film 324 is exposed, aheight difference occurs in some cases in the anisotropic conductor plug327 with respect to the second interlayer insulating film 324, due to adifference in etching rate therebetween but, when the height differenceis not larger than 100 nm (preferably not larger than 50 nm), it doesnot raise any special problem.

After the anisotropic conductor plug 327 is formed, an aluminum film towhich scandium or titanium is added and an ITO film (compound film ofindium oxide and tin oxide) are accumulated thereon. The resultantproduct is subjected to etching to form a pixel electrode 328 made of analuminum film to which scandium or titanium is added and a firsttransparent electrode 329 made of an ITO film. In this embodiment, thepixel electrode 328 and the first transparent electrode 329 constitutean anode 340.

In this embodiment, the thickness of the aluminum film is set to 200 nm,and that of the ITO film 100 nm. The ITO film can be etched with ITO-04N(commercial name of the etching solution for ITO films, manufactured bythe Kanto Kagaku Co., Ltd.), and the aluminum film by a dry etchingmethod using a gas obtained by mixing carbon tetrachloride (SiCl₄) andchlorine (Cl₂).

A sectional view of FIG. 4B of the structure thus obtained correspondsto that of the structure taken along a line A–A′ in FIG. 5A.

Next, as shown in FIG. 4C, an insulating film 330 is formed as a bank.Although, in this embodiment, the bank 330 is formed by using an acrylicresin, it can also be formed by using a silicon oxide film. After thebank 330 has been formed, a surface treatment for the first transparentelectrode 329 is conducted by applying ultraviolet light thereto in anoxygen atmosphere. This treatment has an effect in Increasing a workfunction of the first transparent electrode 329, and, furthermore, aneffect of removing contaminants from the surface thereof.

Organic EL films 331, 332 are then formed to a thickness of 50 nmrespectively. The organic EL film 331 is an organic EL film emittingblue light, and the organic EL film 332 an organic EL film emitting redlight. An organic EL film (not shown) emitting green light is alsoformed at the same time. In this embodiment, the organic EL films areformed separately for each pixel by using an evaporation method using ashadow mask. It is a matter of course that the separate formation of theorganic EL films can also be carried out by suitably choosing a printingmethod and an ink jet method.

In this embodiment, an example using each of the organic EL films 331,332 as a single layer is shown. A laminated structure using CuPc (copperphthalocyanine) as a hole injection layer is also effective. In thiscase, first, a copper phthalocyanine film is formed on the wholesurface, and an organic EL film emitting red light, an organic EL filmemitting green light, and an organic EL film emitting blue light arethen formed for respective pixels corresponding to red, green, and bluecolors.

When a green organic EL film is formed, Alq₃(tris-8-quinolinolatoaluminum complex) is used, and quinacridone orcoumarin 6 is added as a dopant. When a red organic EL film is formed,Alq₃ is used as a matrix material for the organic EL film, and DCJT,DCM1 or DCM2 is added as a dopant. When a blue organic EL film isformed, Balq₃ (5-configuration complex having a mixing ligand for2-methyl-8-quinolinol and a phenol derivative) is used, and perylene isadded as a dopant.

According to the present invention, the organic EL film is not, ofcourse, required to limit to the above-mentioned organic EL film. Aknown low molecular weight organic EL film and a high polymer organic ELfilm can be used. When a high polymer organic EL film is used, a coatingmethod (spin coating method, an ink jet method, or a printing method)can also be used.

After the organic EL films 331, 332 are thus formed, a MgAg film(metallic film obtained by adding 1–10% silver (Ag) to magnesium (Mg))of 20 nm in thickness is formed as a second transparent electrode 333,and, furthermore, an ITO film of 250 nm in thickness as a thirdtransparent electrode 334. In this embodiment, the second and thirdtransparent electrodes 333, 334 constitute a cathode 341.

An EL element 400 made of the anode 340, organic EL film 331 (or organicEL film 332), and cathode 341 is formed. In this embodiment, this ELelement functions as a luminescent element.

Next, as shown in FIG. 4D, an auxiliary electrode 336 made of atransparent conductive film is formed to a thickness of 250 nm on theseal member 335, and an anisotropic conductor 337 made of an anisotropicconductive film on the third transparent electrode 334. The substrate301 and seal member 335 are pasted on each other by using a sealmaterial (not shown).

The pasting step is carried out in an argon atmosphere. As a result,argon is sealed in a space 338. A gas used for sealing may, of course,be any gas as long as it is an inert gas, and a nitrogen gas or a raregas may be used. It is preferable that the space 338 be filled with amaterial absorbing oxygen or water thereinto. It is also possible tofill the space with a resin.

A switching TFT (p-channel type TFT in this embodiment) 401 and acurrent control TFT (p-channel type TFT in this embodiment) 402 areformed by the above-described manufacturing steps. Since all TFTs inthis embodiment are formed of p-channel type TFT, the manufacturingsteps are very simple.

The height-different portions are flattened by the second interlayerinsulating film 324, and the drain wire 321 of the current control TFT402 and the pixel 328 are electrically connected together by using theanisotropic plug 327 buried in the contact hole 325, so that theflatness of the anode 340 is high. Accordingly, the uniformity of thethickness of the organic EL film 332 can be improved, and this enablesthe emission of light from the pixels to become uniform.

[Embodiment]2

In this embodiment, an EL luminescent apparatus having pixels thestructure of which is different from that of the pixels of the ELluminescent apparatus shown in FIG. 2 will be described with referenceto FIG. 7. The embodiment of FIG. 7 can be manufactured, by onlyslightly modifying the structure of FIG. 2, and will be described withattention paid to the points of the former embodiment which aredifferent from the corresponding points of the latter embodiment.Therefore, concerning the parts of the embodiment of FIG. 7 which aredesignated by reference numerals identical with those used in FIG. 2,the statement under “Description of the Preferred Embodiment” may bereferred to.

In the embodiment of FIG. 7, contact holes are formed in an interlayerinsulating film 205, and a pixel electrode 701 and a first transparentelectrode 702 are thereafter formed in the same condition, an insulatingfilm 703 being then formed so as to fill recessed portions due tocontact holes therewith. In this embodiment, the insulating film 703 iscalled a filling insulating film. Since the filling insulating film 703can be formed simultaneously with banks 209, it does not cause thenumber of the manufacturing steps to be increased in particular.

This filling insulating film 703 is formed for the purpose of preventingjust as the anisotropic conductor plugs 206 of FIG. 2 the occurrence ofshort-circuiting of the cathode and the anode ascribed to the recessedportions made of the contact holes. During the formation of the fillinginsulating film 703, a height measured from an upper surface thereof tothat of the second transparent electrode 702 is preferably set to100–300 nm. When this height exceeds 300 nm, it causes theshort-circuiting of the cathode and anode to occur in some cases. Whenthis height becomes not larger than 100 nm, there is a possibility thatthe effect (effect in holding down the influence of electric fieldconcentration in edge portions of the pixel electrode) of the banks 209,which is formed simultaneously with the insulating film 703, lowers.

In this embodiment, a layer of an acrylic resin is formed to a thicknessof 500 nm by a spin coating method after the second transparentelectrode 702 has been formed. The layer of acrylic resin is then etchedwith an oxygen gas turned into plasma, until the thickness of this layer(the portions of the layer in which the contact holes are not provided)amounts to 200 nm. After the thickness of the film is thus reduced, thebanks 209 and the filling insulating films 703 are formed by carryingout a patterning operation.

The construction of an upper surface of a pixel in this embodiment isshown in FIG. 8. Referring to FIG. 8, a sectional view taken along aline A–A′ corresponds to FIG. 7. In FIG. 8, a seal member 215 and ananisotropic conductor 217 are not shown. Since a basic pixel structureis identical with that of FIG. 5, a detailed description thereof isomitted.

As shown in FIG. 8, the bank 209 is formed so as to hide a difference inheight between edge portions of the picture electrode 701 and the anode702, and the filling insulating film 703 is formed by projecting partsof the bank 209. This projecting insulating film has a structure fillingthe recessed portions made of the contact holes of the pixel electrodes701.

The EL luminescent apparatus in this embodiment can be manufacturedeasily by combining the above method of forming the filling insulatingfilm with the manufacturing method of Embodiment 1.

[Embodiment]3

Although only the construction of pixels is shown in the EL luminescentapparatuses shown in the mode of embodiment and Embodiment 1, a circuitfor driving the pixels may be formed in a body on the same substrate. Inthis case, the driving circuit can be formed of an nMOS circuit, a pMOScircuit, or a CMOS circuit. It is, of course, allowable to form thepixel portions alone of TFTs, and use an externally fixed drivingcircuit, typically, an IC tip-including driving circuit (TCP and COG).

In Embodiment 1, the pixel portions are formed by p-channel type TFTsonly, and the number of the manufacturing steps are thereby reduced. Inthis case, it is also possible to form the driving circuit by a pMOScircuit, and use an IC tip-including driving circuit as a drivingcircuit unable to be formed by a pMOS.

The structure of this embodiment can be put into practice by freelycombining the same with the structure of Embodiment 1 or 2.

[Embodiment]4

In this embodiment, an example using an amorphous silicon film as anactive layer of switching TFTs and current control TFTs formed in pixelportions is shown. An inversely staggered TFT is known as a TFT using anamorphous silicon film, and can also be used in this embodiment.

Although a step of manufacturing a TFT using an amorphous film issimple, a size of an element becomes large. In the EL luminescentapparatus according to the present invention, the size of TFT does nothave influence upon the effective emission surface area. Therefore, amore inexpensive EL luminescent apparatus can be manufactured by usingan amorphous silicon film as an active layer.

The structure of this embodiment can be put into practice by freelycombining with any of those of Embodiments 1-3. However, when thestructure of Embodiment 4 is combined with that of Embodiment 3, it isdifficult to manufacture a driving circuit of a high operating speed bya TFT using an amorphous silicon film. Therefore, it is desirable toexternally fix an IC tip-including driving circuit to the structure.

[Embodiment]5

In Embodiments 1–4, active matrix type EL luminescent apparatuses weredescribed. The present invention can also be put into practice withrespect to an EL element of a passive matrix type EL luminescentapparatus.

The structure of this embodiment can be put into practice by freelycombining the same with any of those of Embodiments 1–3. However, whenthe structure of Embodiment 5 is combined with that of Embodiment 3, anIC tip-including driving circuit is necessarily fixed to an outerportion of the structure.

[Embodiment]6

A luminescent apparatus formed by putting into practice the presentinvention can be used as a display of various kinds of electricappliances. The displays formed by inserting a luminescent apparatus ina casing include all information displays, such as a display forpersonal computers, a display for receiving a TV broadcast and a displayfor advertisement.

The electric appliances besides above to which the present invention canbe applied include a video camera, a digital camera, a goggle typedisplay (head mounting display), a navigation system, a music reproducer(car audio and an audio component), a note type personal computer, agame machine, a portable information terminal (mobile computer, aportable telephone, a portable game machine, or an electronic book), andan image reproducer (apparatus adapted to reproduce an image recorded ona recording medium, and an apparatus provided with a display for showingthe image).

As mentioned above, the range of application of the present invention isvery wide, and the present invention can be used for electric appliancesin all fields. The electric appliances in this embodiment may use aluminescent apparatus of any structures shown in Embodiments 1–6.

The present invention is characterized in that an electrode made of atransparent conductive film provided on a seal member is electricallyconnected, by using an anisotropic conductive film, to an electrode madeof a transparent conductive film formed after an organic EL film isformed. This enables a resistance value of the transparent conductivefilm formed after the organic EL film is formed to be substantiallyreduced, and a uniform voltage to be applied to a transparent electrode.

According to the present invention, a luminescent apparatus having agreatly increased effective emission surface area of pixels andreproducing a bright high-quality image can be obtained by employing astructure which has a transparent or translucent cathode and areflecting electrode under an EL element, and which is adapted to takeout the light to the side of the cathode. An electric appliance usingthe luminescent apparatus according to the present invention as adisplay and reproducing an excellent image can also be obtained.

1. A luminescent apparatus comprising: an electro luminescence elementcomprising an electrode having a reflective surface, a transparentelectrode and an organic electro luminescence layer interposedtherebetween; and an auxiliary electrode electrically connected to thetransparent electrode via an anisotropic conductor, wherein thetransparent electrode is formed by laminating a transparent metallicfilm and a transparent conductive film.
 2. A luminescent apparatusaccording to claim 1, wherein the electrode having a reflective surfaceis formed by laminating a metallic film and a transparent conductivefilm.
 3. A luminescent apparatus according to claim 1, wherein theorganic electro luminescence layer is provided in contact with thetransparent metallic film and a transparent conductive film included inthe electrode having a reflective surface.
 4. A luminescent apparatusaccording to claim 1, wherein the transparent metallic film has athickness of 5–70 nm.
 5. A luminescent apparatus according to claim 1,wherein the auxiliary electrode is formed of a transparent conductivefilm.
 6. A luminescent apparatus according to claim 1, wherein theanisotropic conductor comprises a resin in which conductive particlesare dispersed.
 7. A luminescent apparatus according to claim 1, whereinthe luminescent apparatus is an appliance selected from the groupconsisting of a camera, a head mounting display, a navigation system, amusic reproducer, a personal computer, a game machine, a portableinformation terminal, and an image reproducer.
 8. A luminescentapparatus according to claim 1, wherein the transparent metallic film isa film for injecting electrons into the organic electro luminescencelayer.
 9. A luminescent apparatus according to claim 1, wherein thetransparent conductive film is a film for applying a voltage to thetransparent metallic film.
 10. A luminescent apparatus comprising: asubstrate; an electrode having a reflective surface over the substrate;an organic electro luminescence layer over the electrode having areflective surface; a transparent electrode over the organic electroluminescence layer; a plurality of conductors distributed over thetransparent electrode; and an auxiliary electrode over the plurality ofconductors, wherein the auxiliary electrode is electrically connected tothe transparent electrode via the plurality of conductors; and whereinthe transparent electrode is formed by laminating a transparent metallicfilm and a transparent conductive film.
 11. A luminescent apparatusaccording to claim 10, wherein the electrode having a reflective surfaceis formed by laminating a metallic film and a second transparentconductive film.
 12. A luminescent apparatus according to claim 10,wherein the organic electro luminescence layer is provided in contactwith the transparent metallic film and a transparent conductive filmincluded in the electrode having a reflective surface.
 13. A luminescentapparatus according to claim 10, wherein the transparent metallic filmhas a thickness of 5–70 nm.
 14. A luminescent apparatus according toclaim 10, wherein the auxiliary electrode is formed of a transparentconductive film.
 15. A luminescent apparatus according to claim 10,wherein the plurality of conductors comprise a resin in which conductiveparticles are dispersed.
 16. A luminescent apparatus according to claim10, wherein the luminescent apparatus is an appliance selected from thegroup consisting of a camera, a head mounting display, a navigationsystem, a music reproducer, a personal computer, a game machine, aportable information terminal, and an image reproducer.
 17. Aluminescent apparatus according to claim 10, wherein the transparentmetallic film is a film for injecting electrons into the organic electroluminescence layer.
 18. A luminescent apparatus according to claim 10,wherein the transparent conductive film is a film for applying a voltageto the transparent metallic film.
 19. A luminescent apparatuscomprising: a substrate; an electrode having a reflective surface overthe substrate; an organic electro luminescence layer over the electrodehaving a reflective surface; a transparent electrode over the organicelectro luminescence layer; an anisotropic conductor over thetransparent electrode; and an auxiliary electrode formed over theanisotropic conductor, wherein the auxiliary electrode is electricallyconnected to the transparent electrode via the anisotropic conductor;and wherein the transparent electrode is formed by laminating atransparent metallic film and a first transparent conductive film.
 20. Aluminescent apparatus according to claim 19, wherein the electrodehaving a reflective surface is formed by laminating a metallic film anda second transparent conductive film.
 21. A luminescent apparatusaccording to claim 19, wherein the organic electro luminescence layer isprovided in contact with the transparent metallic film and a transparentconductive film included in the electrode having a reflective surface.22. A luminescent apparatus according to claim 19, wherein thetransparent metallic film has a thickness of 5–70 nm.
 23. A luminescentapparatus according to claim 19, wherein the auxiliary electrode isformed of a transparent conductive film.
 24. A luminescent apparatusaccording to claim 19, wherein the anisotropic conductor comprises aresin in which conductive particles are dispersed.
 25. A luminescentapparatus according to claim 19, wherein the luminescent apparatus is anappliance selected from the group consisting of a camera, a headmounting display, a navigation system, a music reproducer, a personalcomputer, a game machine, a portable information terminal, and an imagereproducer.
 26. A luminescent apparatus according to claim 19, whereinthe transparent metallic film is a film for injecting electrons into theorganic electro luminescence layer.
 27. A luminescent apparatusaccording to claim 19, wherein the transparent conductive film is a filmfor applying a voltage to the transparent metallic film.
 28. Aluminescent apparatus comprising: a substrate; a switching TFT over thesubstrate; a current control TFT electrically connected to the switchingTFT; a electrode having a reflective surface over the current controlTFT; an organic electro luminescence layer over the electrode having areflective surface; a transparent electrode over the organic electroluminescence layer; an anisotropic conductor over the transparentelectrode; and an auxiliary electrode over the anisotropic conductor,wherein the auxiliary electrode is electrically connected to thetransparent electrode via the anisotropic conductor; and wherein thetransparent electrode is formed by laminating a transparent metallicfilm and a transparent conductive film.
 29. A luminescent apparatusaccording to claim 28, wherein the electrode having a reflective surfaceis formed by laminating a metallic film and a transparent conductivefilm.
 30. A luminescent apparatus according to claim 28, wherein theorganic electro luminescence layer is provided in contact with thetransparent metallic film and a transparent conductive film included inthe electrode having a reflective surface.
 31. A luminescent apparatusaccording to claim 28, wherein the transparent metallic film has athickness of 5–70 nm.
 32. A luminescent apparatus according to claim 28,wherein the auxiliary electrode is formed of a transparent conductivefilm.
 33. A luminescent apparatus according to claim 28, wherein theanisotropic conductor comprises a resin in which conductive particlesare dispersed.
 34. A luminescent apparatus according to claim 28,wherein the luminescent apparatus is an appliance selected from thegroup consisting of a camera, a head mounting display, a navigationsystem, a music reproducer, a personal computer, a game machine, aportable information terminal, and an image reproducer.
 35. Aluminescent apparatus according to claim 28, wherein the transparentmetallic film is a film for injecting electrons into the organic electroluminescence layer.
 36. A luminescent apparatus according to claim 28,wherein the transparent conductive film is a film for applying a voltageto the transparent metallic film.
 37. A luminescent apparatuscomprising: a plurality of pixels, each of the plurality of pixelscomprising: at least one thin film transistor over a substrate; anelectrode having a reflective surface over the substrate andelectrically connected to the at least one thin film transistor; and anorganic electro luminescence layer over the electrode having areflective surface, a transparent electrode over the plurality ofpixels; an anisotropic conductor over the transparent electrode; and anauxiliary electrode over the anisotropic conductor, wherein theauxiliary electrode is electrically connected to the transparentelectrode via the anisotropic conductor; and wherein the transparentelectrode is formed by laminating a transparent metallic film and atransparent conductive film.
 38. A luminescent apparatus according toclaim 37, wherein the electrode having a reflective surface is formed bylaminating a metallic film and a second transparent conductive film. 39.A luminescent apparatus according to claim 37, wherein the organicelectro luminescence layer is provided in contact with the transparentmetallic film and a transparent conductive film included in theelectrode having a reflective surface.
 40. A luminescent apparatusaccording to claim 37, wherein the transparent metallic film has athickness of 5–70 nm.
 41. A luminescent apparatus according to claim 37,wherein the auxiliary electrode is formed of a transparent conductivefilm.
 42. A luminescent apparatus according to claim 37, wherein theanisotropic conductor comprises a resin in which conductive particlesare dispersed.
 43. A luminescent apparatus according to claim 37,wherein the luminescent apparatus is an appliance selected from thegroup consisting of a camera, a head mounting display, a navigationsystem, a music reproducer, a personal computer, a game machine, aportable information terminal, and an image reproducer.
 44. Aluminescent apparatus according to claim 37, wherein the transparentmetallic film is a film for injecting electrons into the organic electroluminescence layer.
 45. A luminescent apparatus according to claim 37,wherein the transparent conductive film is a film for applying a voltageto the transparent metallic film.
 46. A luminescent apparatuscomprising: a substrate; a first anode and a second anode over thesubstrate with a gap between the first anode and the second anode; afirst organic electro luminescence layer over the first anode; a secondorganic electro luminescence layer over the second anode; a cathode overthe first organic electro luminescence layer and the second organicelectro luminescence layer; and an auxiliary electrode electricallyconnected to the cathode at a portion of the cathode overlying the gap,the auxiliary electrode being electrically isolated from a portion ofthe cathode overlying the first anode.
 47. A luminescent apparatusaccording to claim 46, wherein the cathode comprises a transparent film.48. A luminescent apparatus according to claim 46, wherein the anodecomprises a metallic film.
 49. A luminescent apparatus according toclaim 48, wherein the metallic film has a thickness of 5–70 nm.
 50. Aluminescent apparatus according to claim 46, wherein the organic electroluminescence layer is provided in contact with the cathode and theanode.
 51. A luminescent apparatus according to claim 46, wherein theauxiliary electrode comprises a transparent conductive film.
 52. Aluminescent apparatus according to claim 46, wherein the luminescentapparatus is an appliance selected from the group consisting of acamera, a head mounting display, a navigation system, a musicreproducer, a personal computer, a game machine, a portable informationterminal, and an image reproducer.
 53. A luminescent apparatus accordingto claim 46, wherein the auxiliary electrode is electrically connectedto the cathode via an isotropic conductor.
 54. A luminescent apparatusaccording to claim 46, wherein the auxiliary electrode is provided overthe cathode.
 55. A luminescent apparatus comprising: a substrate; afirst anode and a second anode over the substrate with a gap between thefirst anode and the second anode; an insulating film between the firstanode and the second anode; a first organic electro luminescence layerover the first anode; a second organic electro luminescence layer overthe second anode; a cathode over the first organic electro luminescencelayer, the second organic electro luminescence layer and the insulatingfilm; and an auxiliary electrode electrically connected to the cathodeat a portion of the cathode overlying the gap, the auxiliary electrodebeing electrically isolated from a portion of the cathode overlying thefirst anode.
 56. A luminescent apparatus according to claim 55, whereinthe cathode comprises a transparent film.
 57. A luminescent apparatusaccording to claim 55, wherein the anode comprises a metallic film. 58.A luminescent apparatus according to claim 57, wherein the metallic filmhas a thickness of 5–70 nm.
 59. A luminescent apparatus according toclaim 55, wherein the organic electro luminescence layer is provided incontact with the cathode and the anode.
 60. A luminescent apparatusaccording to claim 55, wherein the auxiliary electrode comprises atransparent conductive film.
 61. A luminescent apparatus according toclaim 55, wherein the luminescent apparatus is an appliance selectedfrom the group consisting of a camera, a head mounting display, anavigation system, a music reproducer, a personal computer, a gamemachine, a portable information terminal, and an image reproducer.
 62. Aluminescent apparatus according to claim 55, wherein the auxiliaryelectrode is electrically connected to the cathode via an isotropicconductor.
 63. A luminescent apparatus according to claim 55, whereinthe auxiliary electrode is provided over the cathode.